Water Borehole Drilling and Installation

Water boreholes are generally drilled to a diameter of 150mm (6”). The hole is drilled using a variety of drilling tools from a simple drag bit through to high impact, high penetration Down The Hole Air Hammers.

The borehole is drilled to the required depth and water levels within the hole are monitored during the drilling. Geologic uses either air flush or mud flush drilling. A majority of the time we use the air flush method. This uses compressed air to drive the drilling tools attached to a rotary drilling rig. The air enables the drilling residue to be driven out of the hole to enable drilling to continue. A by-product of this process is that once the water is found it too is driven out of the hole, the driller monitors the flow of water coming from the hole and uses this data to estimate the water level, quantity and re-charge rate of the borehole.

Depending on the geology being drilled we may have to install temporary steel casing to stop collapses during drilling. These sections of steel casing are screwed together to form a continuous run of casing that supports the side of the borehole and enables drilling to continue into harder and self supporting geology. The requirement for casing can be established from the geological survey information supplied about the site.

Once the borehole is drilled to depth, the tools are removed from the hole, and the borehole is constructed by installing 3 meter lengths of screen and casing with a diameter of 100mm (4”) into the hole. The lower parts of the borehole are created using screen. These are 3 meter lengths of Water Regulation Advisory Scheme (WRAS) approved slotted pipe. These precision cut 1mm slots allow water to percolate into the borehole. The top sections of pipe are solid WRAS approved pipe which prevent any surface water or contamination entering the water supply. The void between the 150mm hole and the 100mm installation is back filled with a recycled glass gravel material. This glass media filter pack serves two purposes, the first of which is to act as an initial water filter, holding any sediment and preventing it from entering the borehole. It also supports the sides of the borehole preventing any collapse. This glass pack is installed to a depth of 6 meters below the surface. The top 6 meter is double lined with a 125mm diameter WRAS approved pipe which is inserted over the 100mm install and acts as a further barrier to prevent surface contamination. This pipe is grouted into place with a bentonite grout being installed both around the outside and between the 100mm and 125mm pipe. This grout seals the pipes in place and prevents movement whilst protecting the installation.

The borehole is then terminated within a purpose made poly well head sump. This is a sealed manhole 600mmx450mm in dimension which is covered with a manhole cover. These can be simple lightweight steel covers through to reinforced weight rated covers to allow traffic to pass over the borehole.

Pump work is installed into the borehole using submersible pumps to supply water for any number of applications. These systems are invariably direct pressure providing water on demand at 3–4bar into a network of new or existing pipe work. These systems can also pump into holding tanks and the water pumped around the network from these tanks.

We will also provide a full chemical suite B water analysis certificate and can design, supply and install water treatment systems to ensure any system supplying potable water (domestic drinking water) meets and exceed the current drinking water regulations.

To provide a quote for drilling we require geological information on the proposed site. If this information is not known by the customer we can prepare a basic geological survey for £65+VAT. All we need for this is the postcode of the site or a map reference/Google Earth pin.

Geologic Boreholes are Corporate Members of the British Drilling Association. We hold both Public and Employers Liability Insurances. All our installations use only the best quality WRAS approved products and equipment. If you require any additional information please contact us.